The use of diesel engines has increased substantially in recent years, particularly in the automotive field. This increased popularity is due to, among other things, improved fuel mileage in comparison to today's standard gasoline engine. In addition, diesel engines typically produce emissions at significant reduced pollutant levels when compared to those of standard gasoline engines. One problem associated with diesel engines, however, is that they have been characteristically difficult to start in cold weather. This is due primarily to an inherent tendency of the diesel fuel to gel in sufficiently cold temperatures, thus causing such starting difficulties. In addition, engines which use fuels in this condition possess a relatively high tendency to stall, even after having been successfully started.
To overcome this problem, fuel line heaters have been utilized, such as the variety that employs a resistance wire wrapped within an insulator. However, heaters of this variety, typically located along the fuel line supplying the engine, have not proven to be very efficient.
In Ser. No. 334,292, filed Dec. 4, 1981 and entitled "Diesel Fuel Heater" (Inventor: David A. Siefer), there is defined a fuel heater which employs at least one positive temperature coefficient thermistor located in the fuel passage of the heater's housing for raising the temperature of the fuel passing therethrough to hopefully reduce gelling. In an application filed concurrently herewith under Ser. No. 490,069, Filed Apr. 29, 1983, entitled "Diesel Fuel Heater and Combined Filter-Heater Assembly" (Inventor: Stephen T. Manchester), there is described a fuel heater which is readily capable of being a retrofit component in many of today's spin-on fuel filter assemblies. Both heaters as described in these applications are compact in design, relatively inexpensive to manufacture, and represent substantial improvements over existing heaters such as those of the resistance variety.
In accordance with the teachings of the instant invention, there is defined a diesel fuel heater which provides a means for enhanced fuel heating in comparison to the designs shown in the described two applications. Specifically, the invention provides a means for collecting a predetermined quantity of fuel within the heater such that this quantity can be heated prior to passage thereof into the filter element. It is thus possible to pass a heated quantity of fuel into the filter and thereby facilitate de-waxing of any gelled fuel therein in comparison to the operation of the heaters described above wherein no such accumulation is provided. Providing such a quantity of fuel also has proven particularly advantageous in a PTC-heated system due to the ability of the captured fuel to provide increased heat sinking, thus increasing power draw by the PTCs and thereby enhancing operation of these devices.
It is believed, therefore, that a diesel fuel heater possessing the above advantageous features as well as others as mentioned hereinbelow would constitute a significant advancement in the art.